a) Field of the Invention
The present invention relates to a laminated semiconductor interconnection wiring structure of a semiconductor device such as a complementary MOS type LSI having regions of opposite conductivity types (n.sup.+ and p.sup.+ regions) to be connected to an electrode.
b) Description of the Related Art
A known conventional complementary MOS type LSI using refractory metal wiring has such a wiring structure as shown in FIG. 5 (for example, refer to JP-A 3-101253).
On the surface of a silicon substrate 10, there are formed a field insulating film 12, a thin insulating film 14, an n.sup.+ -type region 16, a p.sup.+ -type region 18, and other regions (not shown). After forming an insulating film 20 above the substrate, a contact hole is formed in the insulating films 20 and 14 at the area corresponding to the p.sup.+ -type region 18. A polycrystalline silicon layer 22 is then deposited covering the contact hole.
Next, a contact hole is formed through the polycrystalline layer 22 and the insulating films 20 and 14 down to the n.sup.+ -type region 16. A TiN (titanium nitride) layer 24 and a WSi (tungsten silicide) layer 26 are deposited in this order. A resist mask is formed on the WSi layer 26. By using this resist mask, p.sup.+ -type impurity ions are heavily doped selectively into a partial region of the polycrystalline layer 22 via which electrical connection to the p.sup.+ -type region 18 is provided. The partial region of the polycrystalline layer 22 therefore becomes p.sup.+ -type of low resistance. Thereafter, the laminated structure of the polycrystalline layer 22, TiN layer 24, and WSi layer 26 is patterned to leave a wiring layer 28 of a desired pattern.
The TiN layer 24 of the wiring layer functions as an impurity diffusion preventing layer. More particularly, without the TiN layer 24, n.sup.+ -type impurities doped in the n.sup.+ -type region 16 such as phosphorus or arsenic would diffuse laterally from the n.sup.+ -type region 16 to the p.sup.+ -type region 18 via the WSi layer 26 during the thermal treatment at about 800.degree. to 900.degree. C. to be performed after the impurity doping, because the n.sup.+ -type impurities such as phosphorous and arsenic have a high diffusion coefficient in a refractory metal silicide such as WSi. The ohmic contact to the p.sup.+ -type region 18 would therefore be degraded and the contact resistance would increase. In order to prevent the lateral diffusion of n.sup.+ -type impurities, the TiN layer 24 is placed under the WSi layer 26.
With this conventional technique, however, it is difficult to obtain a good ohmic contact to the n.sup.+ -type region 16 because of the direct contact of the TiN layer 24 to the silicon surface. Furthermore, because of the laminated structure of the TiN layer 24 and underlying polycrystalline silicon layer 22, it is necessary to form the contact holes for the regions 16 and 18 at different processing steps, and to selectively dope impurities in the polycrystalline layer 22.